In HIV-infected patients treated with HAART, there are variable rates of reconstitution of T cell numbers and function. An understanding of the mechanisms underlying the recovery of T cells will be important for the design of future strategies to improve T cell reconstitution. The thymus is the organ responsible for producing new naive T cells with a broad immune repertoire from bone marrow-derived precursors. IL-7 is a cytokine that has direct effects upon the thymus and naive T cells. This study examines the role of the thymus in HIV infection and immune reconstitution, and how IL-7 can affect that role.